Furniture is generally delivered in separate parts or bought by the user as a set of prefabricated separate parts so that it may only be assembled in its final place of use and gotten into its condition ready for use. In this respect for the fitters and more particularly for the user, who is generally inexperienced as regards the assembly of furniture, it is desirable for the prefabricated furniture parts such that they may be simply and rapidly assembled and put together as furniture ready for use. A factor which particularly facilitates assembly is the ability to be put together simply and even assembled without the use of tools. It is consequently an objective of fitting manufacturers to supply the furniture industry with attachment elements, which render possible the assembly of prefabricated furniture parts without specialized tools. Thus for example the patent publications DE-C 2,837,327, DE-C 2,905,378 and EP-A 0 610 765 disclose furniture fittings, whose attachment elements may be mounted in suitable pre-drilled holes and may be locked therein by flipping over a lever, that is to say without using a tool.